Improve performance of Activator.CreateInstance #32520
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| Original file line number | Diff line number | Diff line change |
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| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using System.Diagnostics; | ||
| using System.Diagnostics.CodeAnalysis; | ||
| using System.Runtime.CompilerServices; | ||
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| namespace System | ||
| { | ||
| internal sealed partial class RuntimeType | ||
| { | ||
| /// <summary> | ||
| /// A cache which allows optimizing <see cref="Activator.CreateInstance"/>, | ||
| /// <see cref="RuntimeType.CreateInstanceDefaultCtor"/>, and related APIs. | ||
| /// </summary> | ||
| private sealed unsafe class ActivatorCache | ||
| { | ||
| // The managed calli to the newobj allocator, plus its first argument (MethodTable*). | ||
| // In the case of the COM allocator, first arg is ComClassFactory*, not MethodTable*. | ||
| private readonly delegate*<void*, object?> _pfnAllocator; | ||
| private readonly void* _allocatorFirstArg; | ||
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| // The managed calli to the parameterless ctor, taking "this" (as object) as its first argument. | ||
| private readonly delegate*<object?, void> _pfnCtor; | ||
| private readonly bool _ctorIsPublic; | ||
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| #if DEBUG | ||
| private readonly RuntimeType _originalRuntimeType; | ||
| #endif | ||
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| internal ActivatorCache(RuntimeType rt) | ||
| { | ||
| Debug.Assert(rt != null); | ||
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| #if DEBUG | ||
| _originalRuntimeType = rt; | ||
| #endif | ||
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| // The check below is redundant since these same checks are performed at the | ||
| // unmanaged layer, but this call will throw slightly different exceptions | ||
| // than the unmanaged layer, and callers might be dependent on this. | ||
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| rt.CreateInstanceCheckThis(); | ||
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| try | ||
| { | ||
| RuntimeTypeHandle.GetActivationInfo(rt, | ||
| out _pfnAllocator!, out _allocatorFirstArg, | ||
| out _pfnCtor!, out _ctorIsPublic); | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| // Exception messages coming from the runtime won't include | ||
| // the type name. Let's include it here to improve the | ||
| // debugging experience for our callers. | ||
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| string friendlyMessage = SR.Format(SR.Activator_CannotCreateInstance, rt, ex.Message); | ||
| switch (ex) | ||
| { | ||
| case ArgumentException: throw new ArgumentException(friendlyMessage); | ||
| case PlatformNotSupportedException: throw new PlatformNotSupportedException(friendlyMessage); | ||
| case NotSupportedException: throw new NotSupportedException(friendlyMessage); | ||
| case MethodAccessException: throw new MethodAccessException(friendlyMessage); | ||
| case MissingMethodException: throw new MissingMethodException(friendlyMessage); | ||
| case MemberAccessException: throw new MemberAccessException(friendlyMessage); | ||
| } | ||
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| throw; // can't make a friendlier message, rethrow original exception | ||
| } | ||
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| // Activator.CreateInstance returns null given typeof(Nullable<T>). | ||
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| if (_pfnAllocator == null) | ||
| { | ||
| Debug.Assert(Nullable.GetUnderlyingType(rt) != null, | ||
| "Null allocator should only be returned for Nullable<T>."); | ||
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| static object? ReturnNull(void* _) => null; | ||
| _pfnAllocator = &ReturnNull; | ||
| } | ||
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| // If no ctor is provided, we have Nullable<T>, a ctorless value type T, | ||
| // or a ctorless __ComObject. In any case, we should replace the | ||
| // ctor call with our no-op stub. The unmanaged GetActivationInfo layer | ||
| // would have thrown an exception if 'rt' were a normal reference type | ||
| // without a ctor. | ||
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| if (_pfnCtor == null) | ||
| { | ||
| static void CtorNoopStub(object? uninitializedObject) { } | ||
| _pfnCtor = &CtorNoopStub; // we use null singleton pattern if no ctor call is necessary | ||
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| Debug.Assert(_ctorIsPublic); // implicit parameterless ctor is always considered public | ||
| } | ||
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| // We don't need to worry about invoking cctors here. The runtime will figure it | ||
| // out for us when the instance ctor is called. For value types, because we're | ||
| // creating a boxed default(T), the static cctor is called when *any* instance | ||
| // method is invoked. | ||
| } | ||
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| internal bool CtorIsPublic => _ctorIsPublic; | ||
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| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| internal object? CreateUninitializedObject(RuntimeType rt) | ||
| { | ||
| // We don't use RuntimeType, but we force the caller to pass it so | ||
| // that we can keep it alive on their behalf. Once the object is | ||
| // constructed, we no longer need the reference to the type instance, | ||
| // as the object itself will keep the type alive. | ||
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| #if DEBUG | ||
| if (_originalRuntimeType != rt) | ||
| { | ||
| Debug.Fail("Caller passed the wrong RuntimeType to this routine." | ||
| + Environment.NewLineConst + "Expected: " + (_originalRuntimeType ?? (object)"<null>") | ||
| + Environment.NewLineConst + "Actual: " + (rt ?? (object)"<null>")); | ||
| } | ||
| #endif | ||
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| object? retVal = _pfnAllocator(_allocatorFirstArg); | ||
| GC.KeepAlive(rt); | ||
| return retVal; | ||
| } | ||
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| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| internal void CallConstructor(object? uninitializedObject) | ||
| { | ||
| #if DEBUG | ||
| if (uninitializedObject != null && !uninitializedObject.GetType().IsEquivalentTo(_originalRuntimeType)) | ||
| { | ||
| Debug.Fail("Caller passed an unexpected 'this' parameter to ctor - possible type safety violation." | ||
| + Environment.NewLineConst + "Expected type: " + (_originalRuntimeType ?? (object)"<null>") | ||
| + Environment.NewLineConst + "Actual type: " + uninitializedObject.GetType()); | ||
| } | ||
| #endif | ||
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| _pfnCtor(uninitializedObject); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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Is this better than, say:
? I realize the above is probably a bit more IL, but it also means you won't catch and rethrow if the exception didn't match one of the special-cased types. I don't know how common that will be.
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Not ignoring this, but leaving this thread marked unresolved for now because I think we can address it as part of #36194.